Field of the Invention
The invention relates to electro-optic elements and to optical modulators including the same. It relates to electro-optic phase modulation and devices for enabling optical phase, amplitude and intensity modulation. The elements, devices and modulators may find application, e.g., in optical data- and telecommunications, optical storage and optical sensing.
Description of Related Art
Electro-optic modulators, which are used to encode information of electrical data in an optical signal, are key components in photonic links. The requirements of these devices are high speed, low energy consumption, low optical loss, high modulation depth, compact footprint, and dense integration. So far, optical modulators based on functional materials of compound semiconductors, liquid crystals, LiNbO3, or polymer, have been put into practical use. However, these optical modulators are commonly discrete and bulky, which is a consequence of the diffraction limit of light in dielectric media. It is desirable to have a satisfactory chip-scale device solution fulfilling simultaneously all the requirements imposed on optical modulators. Therefore, new optical technologies and optical materials are highly desired and being explored by the research community. As an approach to solve the challenges or the issues, plasmonic devices, which introduce materials with negative dielectric permittivities (more particularly: materials having a permittivity having a negative real part) to localize and guide light, offer deep sub-diffraction limit light confinement and intrinsic broadband behavior. As a result, both low energy consumption benefiting from the enhanced light-matter interaction and small optical device footprints as desired for dense device integration can be achieved. As for the functional optical materials, solid ferroelectric materials, which exhibit large electro-optic effects with fast responses, can be used for fast, integrated and energy-efficient active optical devices. The complex refractive indices of the ferroelectric materials and subsequently the phase and/or amplitude of the incident guided light can be modulated by applying external electrical fields. A combination of both, plasmonic waveguiding mechanism and ferroelectric materials, is a promising technology to realize new-generation optical modulators with a desired and superior device performance.
In Viktoriia E. Babicheva et al., “Bismuth ferrite for active control of surface plasmon polariton modes”, 2014 8th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, 20140825 IEEE, p. 319-321, a plasmonic modulator including a plasmonic waveguide having a bismuth ferrite core that is sandwiched between metal plates, which also serve as electrodes.